silica powder

Silicic acid, silicon dioxide. Along with feldspars, the most common mineral in the Earth’s crust. A weathering product of igneous rock (granite), it occurs in association with clay minerals.
In glazes: the main component of the acidic phase in glazes and frits. A glass-forming agent which, when combined with basic oxides and aluminium oxide, raises the melting point and hardness and imparts lustre. It reduces the AK value and thus helps to prevent hairline cracks.
In masses: A slimming agent; reduces plasticity; increases the sintering and melting ranges; quartz decomposition at 537°C. An important component of porcelain.